Burgess Shale

Pikaia gracilens (a primitive chordate)

Living among the variety of ancestral forms that make up the Burgess Shale community is this earliest known representative of the phylum to which we ourselves belong. Averaging about one and one half inches in length, Pikaia swam above the seafloor using its body and an expanded tail fin. Unfortunately, these features are not properly depicted in this preliminary sketch, the only one available to us. Check the specimen photo below or the illustration of the Burgess Shale Community and see for yourself that the animal was not rounded or earthworm-like as depicted here. The characteristic muscle blocks lying along the centrally important feature, the notochord (or stiffening rod,) are emphasized in the reconstruction.

PLEASE NOTE. Pikaia is not a vertebrate - no one can say if this particular creature is our direct predecessor. Nevertheless, Pikaia is a representative member of the chordate group from which we undoubtedly arose. It resembles a living chordate commonly known as the lancelet.